A mistake I have made before

Speaking of a mistake that I have made before, the first thing comes to my mind is that I've made a bad suggestion to my friend. I remember several years ago, most of my friends were in relationships. I was the only single dog among them. As a saying goes 'The person on the spot is baffled, the onlooker sees clear.', and maybe that's the reason why some of my friends preferred to ask me some for suggestions when they can't stand their boyfriends' behaviors. Most of the time, I would persuade them to reconcile with each other. Sometimes, I would even be the peacemaker. Once, my friend had known her boyfriend cheated on her, but she didn't  have evidence. On one occasion, her boyfriend was caught red handed by her, when he and his lover went shopping. At a result, she broke down. Then she came to me said she needed a shoulder to cry on, and asked me for some suggestions that whether she would continue the relationship with her boyfriend. Honestly, I was in a dilemma, and didn't know what can I say. When she told me she couldn't live without him, I told that he may still loved you, and you should give him another chance. So she made her mind and prepared to throw a surprise party for him, because his birthday was approaching. They got back together at first, but they ended up breaking up. So based on that happened before, I refused to make suggestions about relationship.